Steel is manufactured by "reducing" iron ore in a blast furnace. This process generates scrap and by-products of ores and oxides such as BOF dust, mill scale and the like. Because this scrap and by-products are fine grain and powder-like in size, these particles are too small to be easily used in the steel-making process and typically must be sintered before they are suitable for use in steel-making. Several prior art systems have attempted to reintroduce these particles into a flowing stream of hot metal. Most of the particles which are introduced into the stream merely float on the surface of the stream due to their light weight and slow wetting action. As more particles are added to the stream of hot metal, the particles "freeze up" and form a dam at the area of introduction. Thus, relatively little use of these particles is possible in the manufacture of steel without prior processing of the particles.
My U.S. Pat. No. 3,881,915 ('915) discloses a process for enhancing the reduction of such scrap and by-products added to a molten metal stream by utilizing magnetic forces. The '915 patent discloses a process whereby a substantially continuous charge of metallic particulates is introduced onto the surface of a substantially continuous molten metal stream which flows through a conventional trough. A magnetic field, emanating from beneath the trough and extending through the trough and stream, forces the metal particles into and beneath the surface of the stream and holds them at or beneath the surface until their temperature exceeds the Curie temperature and they are no longer attracted by the magnetic field, thereby accelerating the dissolution or chemical reaction of the particulates by exposure to the heat and movement of the stream.
Conventional troughs are typically comprised of steel and permit only a small portion of the magnetic flux to pass through the trough as the trough itself becomes magnetized. To ensure extension of the magnetic flux through the conventional trough and into the metal stream, a powerful magnetic source must be used. Thus, the magnetic characteristics of conventional troughs render them less than ideal for use in the reduction of metal particulates using magnetic forces.